But experts at the University of Glasgow and pet charity PDSA say passive smoking is even more harmful to animals.

They are now calling on owners to quit their habit.

Research suggests the cancer-causing chemicals contained in cigarettes affect different animals in different ways.

The grooming habits of cats mean they lick the fumes that stick to their fur, increasing their risk of mouth cancers.

Dogs are prone to breathing problems and difficult-to-treat nasal and sinus cancers.

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Dogs exposed to smoking are prone to breathing problems and nasal and sinus cancers

And the sensitive respiratory systems of birds, rabbits and guinea pigs are easily damaged, it is claimed.

PDSA vet Olivia Anderson-Nathan said: “Many pet owners are unaware of the risks that smoking can have on their pets’ health. If they knew, I’m sure they would want to protect them.

“Our vets and nurses regularly see the devastating impact smoking can have on pets.

“Problems range from issues like asthma and chronic coughing through to fatal conditions. Cancers such as lymphoma, for example, are twice as likely in cats exposed to cigarette smoke.”

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Cats lick the smoke fumes that stick to their fur, increasing their risk of mouth cancers

She added: “Studies highlight that this is a really serious issue, and we want pet owners to know that they can make a real difference by simply choosing to smoke outdoors away from their pets.
“If they smoke, their pets smoke, too.”

Professor Clare Knottenbelt, from the University of Glasgow, said previously: “Exposure to smoke in the home is having a direct impact on pets.

“It risks ongoing cell damage, increasing weight gain after castration and has previously been shown to increase the risk of certain cancers.”